The heart is a hollow muscular organ of a somewhat conical form; it lies between the lungs in the middle mediastinum and is enclosed in the pericardium. The heart rests obliquely in the chest behind the body of the sternum and adjoining parts of the rib cartilages, and typically projects farther into the left than into the right half of the thoracic cavity so that about one-third is situated on the right and two-thirds on the left of the median plane. The heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The heart therefore consists of four chambers; the right and left atria, and right and left ventricles, with one-way flow valves between respective atria and ventricles and at the outlet from the ventricles.
Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. Diseased heart valves may be categorized as either stenotic, wherein the valve does not open sufficiently to allow adequate forward flow of blood through the valve, and/or incompetent, wherein the valve does not close completely, causing excessive backward flow of blood or regurgitation through the valve when the leaflets are supposed to coapt together to prevent regurgitation. Valve disease can be severely debilitating and even fatal if left untreated.
As will be explained in greater detail below, the atrioventricular heart valves (i.e., the tricuspid and mitral valves) are located in the center of the heart between the atria and the ventricles of the heart, and play important roles in maintaining forward flow of blood. Atrioventricular valve dysfunction is also commonly known as “regurgitation” and affects well over one million people globally. Heart valve replacement may be indicated when there is a narrowing of a native heart valve, commonly referred to as stenosis, or when the native valve leaks or regurgitates, such as when the leaflets are calcified. When replacing the valve, the native valve may be excised and replaced with either a biologic or a mechanical valve.
Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders. The native heart valves (such as the aortic, pulmonary, tricuspid, and mitral valves) serve critical functions in assuring the forward flow of an adequate supply of blood through the cardiovascular system. These heart valves can be rendered less effective by congenital, inflammatory, infectious conditions, or other disease. Such damage to the valves can result in serious cardiovascular compromise. For many years the definitive treatment for such disorders was the surgical repair or replacement of the valve during, for example, open heart surgery.
Surgical repair of the native valve is commonly conducted using so-called annuloplasty rings. Examples of annuloplasty rings, including methods of use for repairing native valves, are disclosed in U.S. Pat. No. 4,055,861, filed Apr. 9, 1976 and entitled “Support for a Natural Heart Valve”; U.S. Pat. No. 5,041,130, filed Nov. 30, 1989 and entitled “Flexible Annuloplasty Ring and Holder”; U.S. Pat. No. 6,558,416, filed Mar. 6, 2001 and entitled “Annuloplasty Ring Delivery Method”; and in co-pending U.S. patent application Ser. No. 13/019,506, filed Feb. 2, 2011 and entitled “Devices and Methods for Treating a Heart,” the entire contents of each of which are incorporated herein by reference.
In some situations, replacement of the native heart valve with a prosthetic heart valve may be the desired treatment. There are approximately 60,000 mitral valve replacements (MVR) each year and it is estimated that another 60,000 patients should receive a MVR due to increased risk of operation and age. The large majority of these replacements are accomplished through open-heart surgery, where a prosthetic heart valve is surgically implanted. Such surgically implanted prosthetic valves have a long and proven record, with high success rates and clinical improvements noted after such valve replacement. However, sometimes after implantation of a prosthetic heart valve, the heart may reshape itself in a manner which compromises the heart's function. For example, ventricular walls may already be weakened, or may become weakened, with the result that the ventricle becomes enlarged as the walls expand outward.
Although valve regurgitation often occurs due to the dilatation of the valve annulus, mitral and tricuspid valve function and competency frequently depend on the fine geometric and functional integrity of the valve's supporting structures, such as, for example, the associated subvalvular apparatus. The subvalvular apparatus of these heart valves include, among other things, the associated chordae tendinae and papillary muscles. Indeed, the underlying cause of atrioventricular valve dysfunction is sometimes considered to be a dilatation of the associated ventricular chamber (also known as ventricular remodeling), which results in displacement and tethering of the ventricle's papillary muscles. Displacement of these cardiac muscular prominences hampers correct closure of the associated atrioventricular valve during systole and causes valvular insufficiency.
Even if the dysfunctional native heart valve is replaced with a fully functional prosthetic heart valve, ventricular dilatation may already be, or may increase to be, large enough to compromise the efficiency of the pumping action of the heart. A continued progression of ventricular dilatation may end in irreversible ventricular dysfunction or congestive heart failure (CHF). CHF is a family of related conditions defined by failure of the heart to pump blood efficiently. With over one million new cases occurring each year, CHF is considered to be one of the fastest-growing cardiovascular diseases in the world. And, if left untreated, CHF may result in severe lifestyle restrictions and ultimately death. One of the causes of CHF and a very common contributor to the harmful effects of CHF is a dilatated ventricle. Another cause of CHF is Functional/Ischemic Mitral Regurgitation (FIMR). Right heart failure and functional tricuspid regurgitation (FTR) are other disease states of concern.
Thus, what are needed are methods and devices for treating ventricular remodeling and atrioventricular valve regurgitation by addressing the geometric distortion of not only the valve's annulus, but also the supporting structures of the valve.
Additionally, it would be desirable if such a technique could address ventricular remodeling and atrioventricular regurgitation in a single surgery and with a single implant, particularly in patients who are more seriously ill and could benefit most from heart valve repair, but are at greatest risk from repeated bypass.
Further, because damage to heart geometry may be progressive, initial success in reducing regurgitation via heart valve replacement may be followed by further damage to heart geometry via continued ventricular dilatation. It would therefore be desirable to employ approaches to addressing these conditions that are adjustable over time.
Accordingly, further options are needed for valve replacement, particularly for replacement of the mitral and tricuspid valves with associated ventricular treatment.